25 Jan 2019
If the first target creature for Combine Guildmage’s second ability has no +1/+1 counters on it as the ability resolves, nothing happens. The second target creature doesn’t get a +1/+1 counter.
25 Jan 2019
If a creature would normally enter the battlefield with no +1/+1 counters on it, Combine Guildmage’s first ability causes it to enter the battlefield with a +1/+1 counter on it.
25 Jan 2019
If either target creature is an illegal target by the time Combine Guildmage’s second ability tries to resolve, nothing happens. No creature loses or gets a +1/+1 counter.